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Delivery of azithromycin to Chlamydia trachomatis-infected polarized human endometrial epithelial cells by
T R Paul1, S T Knight, J E Raulston
1Department of Microbiology and Immunology, University of North Carolina School of Medicine, Chapel Hill 27599-7290, USA.
Abstract:
An in-vitro model was designed to evaluate whether polymorphonuclear leucocytes (PMN) loaded with azithromycin could migrate and deliver the antibiotic in a bioactive form to chlamydia inclusions in polarized human endometrial epithelial (HEC-1B) cells infected with Chlamydia trachomatis. PMN chemotaxis through the extracellular matrix and between infected epithelial cells was readily observed if the HEC-1B cells had been infected with chlamydiae for 36 or 48 h. Inclusions in infected epithelial cells exposed to PMN loaded with azithromycin were initially distinguished by deformed reticulate bodies and an excessive amount of chlamydial outer membrane vesicles. As the amount of PMN-delivered antibiotic increased, chlamydial inclusions were filled with large cell envelope 'ghosts' which were the remnants of lysed reticulate bodies. The lethal effect of azithromycin was confirmed by a reduction in the viability of infectious progeny. Our results demonstrate that the damage to chlamydiae was due to transport and delivery of azithromycin by PMN to infected genital epithelial cells. When infected HEC-1B cells were exposed to PMN not loaded with the antibiotic, chlamydial morphology was not obviously affected yet few viable progeny could be recovered. In this case, PMN-induced damage to host epithelial cells probably interrupted chlamydial nutrient acquisition and subsequent maturation and formation of infectious progeny.
Insights
Polymorphonuclear leucocytes (PMN) deliver azithromycin to effectively damage Chlamydia trachomatis within host cells. This antibiotic delivery by PMN reduces infectious progeny, demonstrating a novel therapeutic strategy for chlamydial infections.
Area of Science:
- Microbiology
- Immunology
- Pharmacology
Background:
- Chlamydia trachomatis infections are a significant global health concern, often requiring effective antibiotic treatment.
- Polymorphonuclear leucocytes (PMN) play a crucial role in host defense against bacterial pathogens.
- Azithromycin is a key antibiotic used to treat chlamydial infections.
Purpose of the Study:
- To investigate the in-vitro efficacy of azithromycin-loaded PMN in targeting Chlamydia trachomatis within human endometrial epithelial cells.
- To determine if PMN can deliver bioactive azithromycin to chlamydial inclusions.
- To assess the impact of PMN-mediated antibiotic delivery on chlamydial viability and progeny formation.
Main Methods:
- Development of an in-vitro model using polarized human endometrial epithelial (HEC-1B) cells infected with Chlamydia trachomatis.
- Loading of PMN with azithromycin and assessment of their chemotaxis towards infected cells.
- Microscopic evaluation of chlamydial inclusions and morphological changes following exposure to azithromycin-loaded PMN.
- Quantification of infectious progeny to confirm the lethal effect of azithromycin.
Main Results:
- PMN efficiently migrated to and between infected HEC-1B cells, particularly at 36-48 hours post-infection.
- Azithromycin-loaded PMN induced significant morphological damage to chlamydial inclusions, including deformed reticulate bodies and excessive outer membrane vesicles.
- Increased PMN-delivered azithromycin led to the formation of large cell envelope 'ghosts' and a reduction in viable infectious progeny.
- PMN not loaded with azithromycin caused less direct damage to chlamydiae but still reduced progeny, potentially via host cell disruption.
Conclusions:
- PMN can effectively transport and deliver azithromycin in a bioactive form to chlamydial inclusions in infected endometrial epithelial cells.
- PMN-mediated delivery of azithromycin results in the destruction of Chlamydia trachomatis and a significant reduction in infectious progeny.
- This study highlights a potential novel strategy for enhancing antibiotic efficacy against chlamydial infections through PMN-mediated drug delivery.